Use similar interface to access gitolite

Simplified gitolite handle logic
Stubn over monkeypatch
Stub only specific methods in Gitlab:Gitolite
Moved grach auth to lib
added specs for keys observer
removes SshKey role

lib/tasks/gitlab/enable_automerge.rake

@@ -2,9 +2,7 @@ namespace :gitlab do
   namespace :app do
     desc "GITLAB | Enable auto merge"
     task :enable_automerge => :environment  do
-      Gitlab::GitHost.system.new.configure do |git|
-        git.admin_all_repo
-      end
+      Gitlab::Gitolite.new.enable_automerge
 
       Project.find_each do |project|
         if project.repo_exists? && !project.satellite.exists?